Alloy In Simulated Body Fluid Research Articles

Fatigue and corrosion fatigue behaviors of biodegradable Zn-Li and Zn-Cu-Li under physiological conditions

• The fatigue behaviors of biodegradable Zn alloys were investigated. • The corrosion fatigue behaviors of biodegradable Zn alloys were investigated. • The fatigue fracture mode of biodegradable Zn alloys was analyzed. Zinc (Zn) alloys are emerging as a new class of biodegradable metallic materials due to their good biocompatibility, suitable biodegradability, and nontoxicity. However, the dynamic loading in the human body, along with the corrosive physiological environment, brings great challenges to the application of biodegradable Zn alloys. At present, there are few reports on the fatigue and corrosion fatigue properties of Zn alloys in simulated body fluid (SBF). In the present work, extruded Zn-0.8Li and Zn-2Cu-0.8Li alloys were selected in order to systematically evaluate their fatigue and corrosion fatigue behaviors both in air at ambient temperature and in SBF at 37 °C. Results revealed that the fatigue limits of the extruded Zn-0.8Li and Zn-2Cu-0.8Li alloys were about 135 and 180 MPa, respectively, in air at ambient temperature. However, the fatigue limits of the two alloys decreased to 65 and 80 MPa, respectively, in SBF at 37 °C and showed a linear relationship between the corrosion fatigue life and the stress amplitude. The sources of fatigue cracks in air were internal microstructural defects or weak mechanical properties of the material, while the initiation of corrosion pits on the surface was the main reason for the source of the formation of fatigue cracks in SBF. The fracture mode of the extruded Zn-0.8Li and Zn-2Cu-0.8Li alloys was quasi-cleavage fracturing. Compared to static immersion testing, cyclic loading significantly increased the corrosion rates of the two experimental alloys in a corrosion fatigue environment.

Corrosion and wear behavior of Ti–5Cu-xNb biomedical alloy in simulated body fluid for dental implant applications

The present study examined the corrosion and tribological behavior of novel Ti–5Cu-xNb alloy synthesized via powder metallurgy as a new biomedical material in a simulated bodily fluid (SBF) solution. The electrochemical impedance spectroscopy (EIS) study reveals the formation of two protective layers on the surface of alloys during the test. The alloys spontaneously produce a passivating oxide coating on their surfaces, and the breakdown potential (1.14–1.17 V) and re-passivation current density (2.07–3.04 μAcm−2) were observed during the potentiodynamic polarization test. The highest corrosion resistance was observed for the alloy Ti–5Cu–10Nb (icorr = 21.44 nA-cm−2). The SEM and XPS analysis of the corroded surface showed the formation of oxide on the surfaces of the alloys. The samples were tested at 10 N, 15 N, and 20 N loads against the zirconia counterpart to investigate the effect of loading on friction and wear. The lowest coefficient of friction was obtained for Ti–5Cu–5Nb (0.25–0.41) at 20 N loading, while the maximum for Ti–5Cu–10Nb at 15 N load falls in the range of (0.71–0.25). Additionally, they present the wear rate in the range of (5.3 × 10−8-1.45 × 10−6 mm3/mm), in accordance with the change in microstructure and mechanical properties. However, the wear rate increases with the addition of niobium and reaches the maximum for Ti–5Cu–15Nb at 20 N loading condition, but it is relatively deficient compared to commonly used implant material. Therefore, it is suggested that this β-type Ti–5Cu-xNb alloy is a promising candidate, more suitable than the commercially used Ti and Ti–6Al–4V for dental applications.

Corrosion Behavior of Mg-xGd-1Zn-0.4Zr Alloys with Different Gd Additions for Biomedical Application

In recent years, Mg alloys have attracted increased attention for biomedical application owing to their good biodegradability, biocompatibility, and biomechanical properties. However, rapid corrosion is still one of the most common limitations for their implanted application. In this work, the microstructure and corrosion behavior of the solution- and aging-treated Mg-xGd-1Zn-0.4Zr (x = 3, 6, and 9 wt%, denoted as GZ31K, GZ61K, and GZ91K, respectively) alloys were studied using optical microscope (OM), scanning electron microscope (SEM), immersion tests, electrochemical tests, and quasi in situ corrosion method. The results show that block Gd-rich precipitates and needle-like Zr-Zn-rich precipitates are formed as well as α-Mg matrix. With the increase in Gd content, the precipitates increase and the grain size first reduces and then increases. Corrosion experiment results show that the GZ61K alloy has the best corrosion resistance and the GZ91K alloy shows the highest corrosion rate among the three alloys in simulated body fluid (SBF). It is found that α-Mg is preferentially corroded and the precipitates have better corrosion resistance as compared to the α-Mg matrix. The GZ61K alloy with the corrosion rate of 0.23 mm/y in SBF shows a promising prospect for biomedical application.

Effect of pH Value on Wear Behavior of AZ80 Magnesium Alloy in Simulated Body Fluid

Effect of pH Value on Wear Behavior of AZ80 Magnesium Alloy in Simulated Body Fluid

Revealing the mechanical and degradation properties of the Zn-Cu-Ti alloy with ununiform heterostructure

Zn alloy has attracted much attention in recent years as a new biomedical degradable material. However, how to simultaneously achieve its high strength and high ductility is a bottleneck problem to be solved. In this study, the Zn-2.0Cu-0.1Ti alloy with ununiform heterostructure, consisting of the barren areas without CuZn5 phase and the regions enriched with CuZn5 phase, was designed and successfully fabricated through controlled stir casting and hot extrusion. Uniaxial tensile test and Vickers hardness test were applied to reveal the mechanical properties of the Zn-2.0Cu-0.1Ti alloy, while electrochemical test and immersion test were used to characterize its degradation properties. The novel heterostructure was systematically examined by optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM). It was found that the yield strength and ultimate tensile strength of the present Zn-2.0Cu-0.1Ti alloy reach 241.2 ± 4.7 MPa and 265.8 ± 1.3 MPa, showing 294.4% and 230.3% improvement over those of pure Zn. Even more surprising is that the improved strength can be achieved without sacrificing ductility. The substantially increased strength can be mainly attributed to the strengthening mechanisms of grain refinement and Orowan looping, and the maintenance of good ductility thanks to the excellent dislocation storage ability of the present heterostructure. At the same time, the corrosion rate of the alloy in simulated body fluids also reaches the industry standard for orthopedic implants. This study not only sheds light on the design and fabrication of Zn-based material for surgical implantation application but also provides a feasible route to improve the mechanical properties of other precipitates reinforced alloys.

Chemical, Electrochemical, and Surface Morphological Studies of the Corrosion Behavior of the AZ31 Alloy in Simulated Body Fluid: Effect of NaOH and H2O2 Surface Pretreatments on the Corrosion Resistance Property.

Magnesium and its alloys have attracted attention for biomedical implant materials in dental and orthopedic applications because of their biodegradability and similar properties to human bones. The very high rate of degradation in the physiological systems is, however, a major setback to their utilization. Chemical modification is one of the approaches adopted to enhance the corrosion resistance property of Mg and its alloys. In this work, NaOH and H2O2 were used as a pretreatment procedure to improve the corrosion resistance of the AZ31 Mg alloy in simulated body fluid (SBF). Advanced techniques such as dynamic electrochemical impedance spectroscopy (dynamic-EIS), atomic force microscopy, and optical profilometry were used in addition to the classical mass loss, hydrogen evolution, EIS, and polarization techniques to study the corrosion resistance property of the alloy in SBF for 30 h. Results obtained show that the surface treatment significantly enhanced the corrosion resistance property of the alloy. From dynamic-EIS at 30 h, the charge transfer resistance of the untreated AZ31 Mg alloy is 432.6 Ω cm2, whereas 822.7 and 2617.3 Ω cm2 are recorded for NaOH- and H2O2-treated surfaces, respectively. H2O2 is a better treatment reagent than NaOH. The mechanism of corrosion of both untreated and treated samples in the studied corrosive medium has been discussed.

Ultrafast flame coating of carbon and chemical vapor deposition of graphene on NiTi alloy to enhance its corrosion resistance

To study their surface protection performance, both graphene and carbon layers have been deposited onto the surface of NiTi alloy via the common chemical vapor deposition (CVD) and a facile flame coating technique, respectively. The latter can be accomplished within tens of seconds with the combustion flame itself as the carbon source and alloy substrate as catalyst. The carbon layer not only inhibits effectively the Ni2+ releasing from NiTi alloy, but also displays lower surface roughness and higher corrosion resistance than that of the graphene coating. The effect of the flame coating time on the performance of resulted carbon layer has been studied comprehensively. The lowest corrosion current density (1.6 μA/cm2) of the flame coated alloy in simulated body fluid has been achieved by adjusting the flame time to be just 30s. This value is much less than that of graphene coating (2.4 μA/cm2) in the same test conditions. And it gets even less in 3.5 wt% NaCl solution (1.3 μA/cm2), implying the potential application of the flame coating method for more corrosive marine environments. Also, the Ni2+ releasing concentration of NiTi/C-30s is decreased to be around one fourth that of bare NiTi. Moreover, the excellent scratch resistance of the carbon layer and its strong adhesion to NiTi substrate have been also confirmed by both the cross-cut and scratching tests. Furthermore, both the elastic modulus and hardness of the alloy decreased marginally after the fast and mild-temperature flame coating process according to the nano-indentation test results. Compared with traditional surface engineering approaches, the flame coating method has many advantages, such as simple and fast process, high protective performance, environmental-friendly fabrication and protection. All of these benefit its promising application in various fields.

The Effect of Electronic Properties of Anodized and Hard Anodized Ti and Ti6Al4V on Their Reactivity in Simulated Body Fluid

The electronic properties of barrier and porous layers on Ti and Ti6Al4V were studied. Barrier anodic oxides grown to 40 V on Ti and on Ti6Al4V are both n-type semiconductors with a band gap of 3.3 eV and 3.4 eV respectively, in agreement with the formation of amorphous TiO2. Anodizing to 200 V at 20 mA cm−2 in calcium acetate and β-glycerol phosphate disodium pentahydrate leads to the formation of Ca and P containing porous films with a photoelectrochemical behaviour dependent on the metallic substrate. A band gap of 3.2 eV and the flat band potential of −0.5 V vs Ag/AgCl were measured for the porous oxide on Ti, while optical transitions at 2.15 eV and a significantly more positive flat band potential were revealed for the porous oxide on the alloy. The different electronic properties were rationalized by taking into account the presence of localized states inside the gap, induced by incorporation of Al and V from the underlaying alloy during the hard anodizing process. These electronic properties are responsible of the reactivity of porous layer grown on Ti6Al4V alloy in simulated body fluid.

The influence of cathodic potentials on the surface oxide layer status and tribocorrosion behaviour of Ti6Al4V and CoCrMo alloys in simulated body fluid

Ti6Al4V and CoCrMo alloys are important metallic materials in orthopaedics applications because of their excellent combination of corrosion resistance, mechanical properties, and biocompatibility. However, Ti6Al4V possesses poor wear resistance, and CoCrMo implants have been reported to release toxic ions in vivo. In addition, orthopaedics applications are subjected to corrosive media and cyclic stresses, increasing the likelihood of scratching the surface, removing the protective oxide film, and thereby causing cathodic polarisation of the system. The present work examined the material loss in tribocorrosion and the thickness and resistivity (status) of the oxide layer under different cathodic potentials. The cathodic polarisation conditions were chosen to reflect those that might be found in vivo. The results explicitly showed a different impact of the cathodic potentials on the tribocorrosion behaviour of the two materials.

An eco-friendly Ca[sbnd]Ce and Ca[sbnd]Y based LDH coating on AZ31 Mg alloy: Surface modification and its corrosion studies in simulated body fluid (SBF)

The corrosion resistance of AZ31 is inappropriate, which demands the improvement of the anti-corrosion performances for practical applications. Therefore, environmentally friendly rare earth elements based such as CaCe and CaY layered double hydroxide (LDH) coatings are developed on the AZ31 alloy surface in this work. The coatings are characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and the static sessile drop method as well as electrochemical measurements. The results show that these two kinds of LDH coating can obviously retard the corrosion of AZ31 in simulated body fluid (SBF). Also, precipitation of the corrosion products synergistically improves the self-healing and protection performances. However, the CaY based layers contain some cracks that limit the superior protection performance of the coating. The CaCe based LDH coating shows a significantly enhanced corrosion resistance with the corrosion current density of 0.058 μA·cm−2 which is prepared in the solution containing the Ca and Ce cations with the 2:1 mol ratio. It opens the possibility to improve the service life of AZ31 magnesium alloy in SBF.

Understanding the effects of excimer laser treatment on corrosion behavior of biodegradable Mg-1Ca alloy in simulated body fluid

In this study, a KrF excimer laser was used to modify the biodegradable Mg-1Ca alloy and the time-evolution degradation behavior of the alloy before and after laser treatment was investigated in simulated body fluid (SBF) solution using immersion tests and electrochemical impedance spectroscopy (EIS). A 5 µm melted layer with a homogeneous microstructure and an MgO film on the surface were achieved by laser radiation. Corrosion observations (hydrogen evolution, morphology and corrosion products) and EIS results revealed an improvement of corrosion resistance after laser treatment for 48 h. It was found a two-layer structure developed after 2 h immersion on both the untreated and laser-treated alloys, but the sequence of forming the two layers was opposite and greatly influenced by the laser-treated layer. The time-evolution corrosion processes on the untreated and laser-treated alloys were discussed, providing a better understanding of corrosion behavior of biodegradable Mg alloys modified by excimer laser.

Understanding the Corrosion Behavior of the AZ91D Alloy in Simulated Body Fluid through the Use of Dynamic EIS.

Dynamic electrochemical impedance spectroscopy (dynamic EIS) has the capacity to track changes on surfaces in a changing corrosive system, an advantage it holds over classical EIS. We used the dynamic EIS approach to provide insight into the corrosion behavior of the AZ91D Mg alloy in simulated body fluid for 30 h at 25 °C. The results reveal that the impedance response of the alloy is influenced by the immersion time. Between 0 and 7 h, impedance with three time constants was obtained, whereas two-time-constant impedance spectra were obtained between 8 and 30 h of immersion. The results confirm the breakdown of the corrosion product at longer immersion times.

In Vitro Corrosion Behavior of Zn3Mg0.7Y Biodegradable Alloy in Simulated Body Fluid (SBF)

Biodegradable metallic materials represent a new class of biocompatible materials for medical applications based on numerous advantages. Among them, those based on zinc have a rate of degradation close to the healing period required by many clinical problems, which makes them more suitable than those based on magnesium or iron. The poor mechanical properties of Zn could be significantly improved by the addition of Mg and Y. In this research, we analyze the electro-chemical and mechanical behavior of a new alloy based on Zn3Mg0.7Y compared with pure Zn and Zn3Mg materials. Microstructure and chemical composition were investigated by electron microscopy and energy dispersive spectroscopy. The electrochemical corrosion was analyzed by linear polarization (LP), cyclic polarization (CP) and electrochemical impedance spectroscopy (EIS). For hardness and scratch resistance, a microhardness tester and a scratch module were used. Findings revealed that the mechanical properties of Zn improved through the addition of Mg and Y. Zn, Zn-Mg and Zn-Mg-Y alloys in this study showed highly active behavior in SBF with uniform corrosion. Zinc metals and their alloys with magnesium and yttrium showed a moderate degradation rate and can be considered as promising biodegradable materials for orthopedic application.

A heterogeneous TiO2/SrTiO3 coating on titanium alloy with excellent photocatalytic antibacterial, osteogenesis and tribocorrosion properties

In order to meet the clinical demand for titanium implants, the heterogeneous structure of TiO2/SrTiO3 coating was in situ fabricated on the surface of Ti6Al4V alloy by a facile way. The well-designed Ti6Al4V/TiO2/SrTiO3 composite exhibits a strong photocatalytic antibacterial efficiency against Escherichia coli (E. coli). The suitable energy band structure, improved light absorption and enhanced carrier separation of TiO2/SrTiO3 heterojunction facilitate the generation of bactericidal reactive oxygen species (ROS) under the illumination of UV light. The biocompatible SrTiO3 component effectively favors the adhesion, proliferation and osteogenic differentiation of human bone mesenchymal stromal cells (hBMSCs) in vitro. It is worth noting that the dense oxide coating provides a reliable barrier against tribocorrosion for the titanium alloy substrate, and the wear volume loss of the Ti6Al4V/TiO2/SrTiO3 reduces to 1/8 of that of the bare Ti6Al4V alloy in simulated body fluid. In this work, a multifunctional coating system was proposed to provide inspiration for the development of novel artificial bone implant materials.

Corrosion behavior of Ag-based alloy in simulated body fluid solution

Ag-based alloys are vital for joining bioceramics for implantable devices. However, rare research has conducted systematic studies on the biocompatibility of Ag-based alloys. Herein, the corrosion behaviors of two kinds of Ag-based alloys (AgCuTi and AgCu) in simulated body fluid are analyzed in detail through systematic electrochemical measurements. The corrosion resistance of these two alloys shows first increasing and then decreasing tendency with increasing corrosion time. The corrosion process of the AgCu alloy clearly shows the dissolution and deposition phenomenon, while the corrosion reaction of AgCuTi alloy is derived by deposition process. Further, during the corrosion process, AgCuTi alloy leaches less Cu and can produce some calcium phosphate. This study provides some instructional views on reliable joining of biomaterials.

Improved corrosion protective performance of chitosan coatings reinforced with nano-ZnO on degradable magnesium alloy in simulated body fluid

Improved corrosion protective performance of chitosan coatings reinforced with nano-ZnO on degradable magnesium alloy in simulated body fluid

In vitro degradation behavior of novel Zn–Cu–Li alloys: Roles of alloy composition and rolling processing

Zn–alloys are considered to be promising biodegradable materials due to suitable degradation rates. In this paper, novel Zn–Cu–Li alloys with layered CuZn4 structure were achieved. The corrosion properties of newly developed biodegradable Zn–Cu–Li alloys in simulated body fluid was studied. Results indicated that the cold-rolled alloys presented a relatively uniform corrosion mode, although early corrosion occurred preferentially at phase boundaries. Galvanic corrosion and corrosion product films jointly determined the later corrosion process. Cu improved the corrosion potential and film properties in its solid solution state, induced galvanic corrosion, and provided a physical barrier to corrosion by forming CuZn4 phase. Rolling accelerated the initial corrosion rate by enhancing the matrix electrochemical activity, while it contributed to uniform corrosion by improving the CuZn4 phase shape. Finally, cold-rolled Zn–4Cu–0.02Li possessed the best corrosion resistance and mechanical properties combination among the prepared alloys, with a yield strength of 256 MPa, an ultimate strength of 342 MPa, a fracture elongation of 39.8 %, and a corrosion rate of nearly 55 μm/year.

Micro-abrasion of medical NiTi alloy as artificial prosthesis in simulated body fluid

The micro-abrasion of medical NiTi alloy in simulated body fluid was investigated in this paper. The friction and wear tests were carried out by TE66. The surface morphology of wear scar and the wear mechanism were examined by SEM. The wear rates were calculated according to the equations. The effects of load, type and size of wear particles were considered. Under the same wear particle, the wear particle size has little influence on the wear rate. The wear rates caused by SiC particle are greater than that caused by Al2O3 particle. Under the experimental conditions, the lowest wear rate of 2.3×10-5mm3/Nm is obtained at the particle size of SiC F1200 and the load of 2.0N. The abrasive wear was the dominant wear mechanism.

Duty cycle influence on the corrosion behavior of coatings created by plasma electrolytic oxidation on AZ31B magnesium alloy in simulated body fluid

Ceramic coatings were applied on the surface of AZ31 Mg alloy using plasma electrolytic oxidation procedure with distinct duty cycles (20%, 50%, and 80%) by a direct current mode in an alkaline electrolyte. The influence of the duty cycle on the corrosion performance of the coatings was studied in addition to their microstructures. In order to evaluate the corrosion performance of created coatings in different duty cycles, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) measurements were measured in simulated body fluid (SBF). The surface properties and chemical compositions of the coatings were evaluated by X-ray diffraction pattern and scanning electron microscopy. The results indicated that in the higher duty cycles (80%), the created coating had a uniform surface with a lower porosity percentage and a higher thickness. The highest corrosion resistance arose from the least corrosion current density (6.46 ×10−6µA cm−2) of the produced coating in the higher duty cycles (80%).

In Vitro Degradation Behavior of Ti-Microalloyed AZ31 Magnesium Alloy in Simulated Body Fluid

In Vitro Degradation Behavior of Ti-Microalloyed AZ31 Magnesium Alloy in Simulated Body Fluid